A symmetry-based analysis of Raman and infrared spectra of the compounds (poly(ethylene oxide))(3)LiCF3SO3 and (poly(ethylene oxide))NaCF3SO3

A symmetry-based factor group analysis is applied to the crystalline compou nds (PEO)(3)LiCF3SO3 and (PEO)NaCF3SO3, focusing on the vibrational modes o riginating in the intramolecular motion of the triflate anion. The dynamic coupling of the triflate anions in the unit cell yields a vibrational multi plet whose components exhibit different spectral activities. Experimentally , the Raman and IR spectra of the two compounds display multiple bands in t he nu (s)(SO3) and delta (s)(CF3) spectral regions. In the delta (s)(CF3) s pectral region of each compound, the frequencies of the Raman and IR bands are non-coincident and differ by similar to5 cm(-1). The frequency differen ce indicates a modest amount of dynamical coupling between the triflate ani ons in the crystal. The spectroscopic analysis of other modes such as delta (as)(CF3), delta (s)(SO3), and delta (as)(SO3) provides useful information about ionic interactions in the crystalline compounds. (C) 2000 Elsevier S cience B.V. All rights reserved.